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DP83848I: Internal circuit of RESERVE pin

Guru 13295 points

Part Number: DP83848I

Hi

The customer has questions for RESERVE pin (PIN20, PIN21).

Could you please answer followings?

1.

According to datasheet, these pins must be pulled up through 2.2K resistor to AVDD33.

Why isn't it allow to connect these pins to GND or leave them float?

2.

The customer want to leave pins open if possible.

What impact could it be considerable if these are open?

BestRegards

  • Hi na na,

    There is detect functionality in the reserved pins 20 & 21 that could put the PHY into an undefined operational state. An old function was planned, but never implemented, and this function must not be enabled.

    So the reserved pins MUST be pulled up to AVDD33.

    Best Regards,

    Rob Rodrigues

    EFL (Ethernet & FPD Link) Applications Engineer

  • Guru 13295 points

    In reply to Rob Rodrigues:

    Hi Rob

    Thank you for your reply.

    The customer asked one more question.

    Additional questions:

    RESERVED pins are defined as input/output.

    Is there a way to set RESERVE pin as output by register control? (e.g. by using MDIO)

    BestRegards

  • In reply to na na78:

    Hi na na,

    The I/O nature of the pins cannot be changed.

    Best,

    Rob Rodrigues

    EFL (Ethernet & FPD Link) Applications Engineer

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